JPS6010379B2 - magnetic recording and reproducing device - Google Patents

Description

Detailed Description of the Invention The present invention includes a first motor that drives a capstan that transports a magnetic tape at a constant speed, and a reel stand that winds the magnetic tape that is transported at a constant speed by the capstan onto a take-up reel. The present invention relates to a magnetic recording/reproducing device having a second motor that drives the magnetic recording/reproducing device.

In general, in magnetic recording and reproducing devices in which the capstan and reel stand are driven by separate motors during recording and playback, torque fluctuations in the motor that drives the reel stand are directly transmitted as tape tension fluctuations on the take-up side, which can cause wow and flutter. This was one factor. To solve this problem, it would be possible to use a motor with small torque fluctuations to drive the reel stand, but this would have been expensive and could not be used in popular machines. For this reason, generally, a slip mechanism made of felt and springs is interposed between the reel stand and the motor to reduce fluctuations in tape tension on the take-up side due to fluctuations in motor torque. This had the disadvantage that the transmission torque of the mechanism changed, making the magnetic tape winding torque unstable during recording and playback. The present invention provides a magnetic recording/reproducing device that completely eliminates these drawbacks with a simple mechanism.

An embodiment of the present invention will be described below with reference to the drawings. In the figure, a cassette 2 contains a magnetic tape 8 wound around a pair of supply reels 4 and a take-up reel 6.

A pull-out pin 1 pulls out the magnetic tape 8 from inside the cassette 2 and brings it into contact with an erasing head 12 and a recording/reproducing head 14 fixed to a pull-out board (not shown). capstan 16
is rotated counterclockwise in FIG. 1 by a first motor 18 attached below a substrate (not shown). The two pinch rollers are configured to be able to reciprocate between a position within the cassette 2 and a position where the magnetic tape 8 is pressed onto the capstan 16. A supply V-supply reel stand 24 that engages with the supply reel 4 and rotates as a unit is rotatably attached to a pin 22 that stands up on the board (not shown). A take-up reel stand 28, which engages with the take-up reel 6 and rotates as a unit, is rotatably connected to the pin 26 standing in the shield. The motor pulley 3 is fixed to the main shaft of a second motor 32 attached to the lower part of a board (not shown). Idler-3
4 is rotatably mounted on a shaft 38 which is mounted on a sliding plate 36 which is arranged on a circuit board so that it can be moved, and when recording and playing back a well-known motor The comb is made so that the angle of combing is approximately 115 degrees.
Next, the operation will be explained.

During recording and playback, the magnetic tape 8 pulled out of the cassette 2 by the pull-out pin 10 and the pinch roller 20 is brought into contact with the erasing head 12 and the recording/playback head 14, and the magnetic tape 8 is pulled out of the cassette 2 by the cooperation of the capstan 16 and the pinch roller 20. It is transferred at a constant speed to the right in Figure 1. On the other hand, since the second motor 32 is rotating clockwise in FIG. 1, the motor pulley 30 is also rotating clockwise in FIG. The magnetic tape 8 rotates clockwise in FIG.
Roll up. At this time, as is well known, the capstan 16
A winding tension is generated on the magnetic tape 8 between the magnetic tape 8 and the winding reel 6, and if this winding tension fluctuates greatly, wow and flutter will worsen. One of the major causes of the fluctuation in the winding tension is the fluctuation in the torque of the second motor 32. In the case of a general DC micromotor, when the brushes are in pairs and the number of commutator divisions (hereinafter referred to as the number of poles) is p, a torque fluctuation of 2xp occurs per revolution. Now, the magnetic tape feeding speed of the capstan 16 is v, the radius of the magnetic tape roll wound on the take-up reel 6 is R, and the reduction ratio between the motor pulley 30 and the take-up reel stand 28 (= When the number of rotations n of the second motor 32 is niVX support [rpS], the torque fluctuation frequency fT of the second motor 32 is f, = or Xn. =NiteヱX poison [HZ], which changes with the radius R of the magnetic tape roll wound on the take-up reel 6.

In this embodiment, v=9.53's, p=3' p=3 poles, and R changes from 1.5 arcs to 4 arcs, so the torque fluctuation frequency f of the second motor 32 is As shown by curve A in Figure 2, the frequency gradually decreases from 18.2 [Hz] at the beginning of winding as the radius R of the magnetic tape roll increases.

On the other hand, since the magnetic tape 8 between the capstan 16 and the take-up reel 6 is an elastic body, the equivalent moment of inertia of the rotating body that engages with the take-up reel 6 and rotates around the rotation axis of the take-up reel 6 is It has a unique resonant frequency. Now, assuming that the elongation coefficient of the magnetic tape 8 is 1/8 and the length of the magnetic tape between the capstan 16 and the take-up reel 6 is 1, the length of the magnetic tape between the capstan 16 and the take-up reel 6 is The spring constant k is k=÷needle skin.

Also, the radius of the take-up reel 6 is taken as the radius, and the take-up reel 6
If the radius of the magnetic tape roll wound on is R, then
The moment of inertia Jt of this magnetic tape roll is JF (R4-M).

Here, y is the density of the magnetic tape 8, and the magnetic tape 8 of this embodiment has a thickness of 18 mm, a width of 0.63 mm, and is coated with a magnetic material of y-Fe203, y = 1.7 x 10-3. Bait-s2 one arc-4. B is the width of the magnetic tape 8, B=0.63c
It is. When the total moment of inertia of the take-up reel 6 and the take-up reel stand 28 is JR, and the total moment of inertia of the motor pulley 30 and the rotor of the second motor 32 is JM, it engages with the take-up reel 6 and rotates. The equivalent moment of inertia J around the rotational axis of the take-up reel 6 of the rotating body is J
=Jt+JR1p2JM.

(The moment of inertia of the idler 34 is omitted.)
Therefore, the resonance frequency of the magnetic tape 8 between the capstan 16 and the take-up reel 6 is k;
It can be seen that it changes with

In this embodiment, the radius R of the magnetic tape roll wound on the take-up reel 6 varies from 1.5 mm to 4 mm, so the moment of inertia Jt of the magnetic tape roll varies from 0.422 mm to 0.422 mm. Changes to skin-s2.

In addition, in this embodiment, the length of the magnetic tape between the capstan 16 and the take-up reel 6 is about 1 mm, and although it becomes a little shorter as the radius R of the magnetic tape roll increases, the rate of change is small, so it remains constant. consider The elongation coefficient of the magnetic tape 8 of this example was about 2×10-51/gr. The total moment of inertia JR of the take-up reel 6 and the take-up reel stand 28 is 0.1
The total moment of inertia JM of the motor pulley 30 and the rotor of the second motor 32 is 0.02r.
-arc-s2. As a result, the resonance frequency fo of the magnetic tape 8 between the capstan 16 and the take-up reel varies from 31.9 [HZ] at the beginning of winding to the radius R of the magnetic tape roll, as shown by curve B in FIG. Increase gradually as the amount increases. As can be seen from FIG. 2, curves A and B never intersect, so the torque fluctuation frequency fT of the second motor 32 and the magnetic tape 8 between the capstan 16 and the take-up reel 6 from the start of winding to the end of winding. The resonant frequencies M of the two do not match. If only the reduction ratio p is changed to 5 under the same conditions as above, the torque fluctuation frequency fT of the second motor 32 is calculated in the same way as above, and as shown in curve C in Fig. 2, it becomes 3 at the beginning of winding.
It gradually decreases from 0.3 [HZ] as the radius R of the magnetic tape roll increases.

In addition, the resonance frequency of the magnetic tape 8 between the capstan 16 and the take-up reel 6 now varies from 21.8 [HZ] at the beginning of winding to the radius R of the magnetic tape roll, as shown by curve D in FIG. Since it gradually increases as the curve C and curve D increase, R=
1. Intersect near &ne.

That is, around R=1.8, the torque fluctuation frequency fT of the second motor 32 and the resonance frequency fo of the magnetic tape 8 between the capstan 16 and the take-up reel 6 match, and the winding tension of the magnetic tape 8 fluctuates. The rate increases dramatically. In the experiment, the fluctuation rate of the winding tension in the case of no resonance was 5 to 100 degrees, and the wow and flutter became considerably worse. As described above, when the torque fluctuation frequency f of the second motor 32 that drives the take-up reel stand 28 and the resonance frequency of the magnetic tape 8 between the capstan 16 and the take-up reel 6 match,
The torque fluctuation of the second motor 32 is amplified, resulting in a winding tension fluctuation of the magnetic tape 8, which worsens wow and flutter.

However, in the magnetic recording/reproducing device according to the present invention, the second
The torque fluctuation frequency fT of the motor 32 is
It gradually decreases as the radius R of the upper magnetic tape roll increases,
Focusing on the fact that the resonance frequency fo of the magnetic tape 8 between the capstan 16 and the take-up reel 6 gradually increases as the radius R of the magnetic tape roll on the take-up reel 6 increases, Since the torque fluctuation frequency f' of the motor 32 is set to be smaller than the resonance frequency fo of the magnetic tape 8 between the capstan 16 and the take-up reel 6 at the beginning of winding, both frequencies fT and W are absolutely No match, magnetic tape 8
The resonance phenomenon does not occur and stable performance can be obtained.
From the above, the torque fluctuation frequency f of the second motor 32 at the end of winding is equal to the resonance frequency fo of the magnetic tape 8 between the capstan 16 and the take-up reel 6 at the end of winding.
It goes without saying that even if the frequency fT and fo are made larger, the frequencies fT and fo will never match.

[Brief explanation of drawings]

FIG. 1 is a plan view showing a configuration example of a magnetic recording/reproducing apparatus of the present invention, and FIG. 2 is a diagram showing a frequency change curve with respect to the tape roll radius on the winding side of the same apparatus. 6... Winding side reel, 8... Magnetic tape, 16
...Capstan, 18...First motor, 20...
... Pinch roller, 28 ... Take-up reel stand, 30 ... Motor pulley, 32 ... Second motor, 34
...Idora. Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1. A magnetic recording and reproducing device that winds a magnetic tape transferred at a constant speed using a capstan and a pinch roller onto a take-up reel, comprising: a first motor that drives the capstan;
A take-up reel stand that engages with the take-up reel and rotates as one unit without slipping, a second DC motor that drives the take-up reel stand, and the second DC motor during recording and playback. comprising a deceleration means for decelerating the rotation of the second reel and transmitting it to the take-up reel stand without slipping;
equivalent inertia around the rotation axis of the take-up reel of the DC motor, the speed reduction means driven by the second DC motor, the take-up reel stand, the take-up reel, and the magnetic tape roll wound on the take-up reel; The resonant frequency caused by the moment and the magnetic tape from the capstan to the take-up reel and the torque fluctuation frequency of the second DC motor start winding the magnetic tape onto the take-up reel during recording and playback. A magnetic recording/reproducing apparatus characterized in that the reduction ratio of the reduction means is set so that the reduction ratio does not match between the time when the winding ends and the time when the winding ends. 2. The second DC motor, the deceleration means driven by the second DC motor, the take-up reel stand, the take-up reel, and the take-up at the time of starting to wind the magnetic tape on the take-up reel during recording and playback. The resonance frequency caused by the equivalent moment of inertia of the magnetic tape roll wound around the reel around the rotation axis of the take-up reel and the magnetic tape between the capstan and the take-up reel is the same as that of the second DC motor. 2. The magnetic recording and reproducing apparatus according to claim 1, wherein the torque fluctuation frequency is greater than the torque fluctuation frequency of . 3. The second DC motor, the deceleration means driven by the second DC motor, the take-up reel stand, the take-up reel, and the take-up at the time of finishing winding the magnetic tape on the take-up reel during recording and playback. The resonance frequency caused by the equivalent moment of inertia of the magnetic tape roll wound around the reel around the rotation axis of the take-up reel and the magnetic tape between the capstan and the take-up reel is the same as that of the second DC motor. 2. The magnetic recording/reproducing apparatus according to claim 1, wherein the torque fluctuation frequency is smaller than the torque fluctuation frequency of .